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jojjelito

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  8. jojjelito

    Posted

    Hola stiltz&Rumpel,

    I've heard plenty of filters but I think you're on to something: the top 5 analogs are the Minimoog VCF, Korg's early MS-20/MS-10, the dual CEM-3350 of the Syrinx, the OSCar and Thomas Henry's Mankato. But there's plenty of good stuff out there :afro:

    The CEMs... what can I say? She's at a nice age, ripe age, ready to be killed by the thrill :poke:

    PS: You get brownie points for the lyrics reference (don't Google-cheat!)

  9. jojjelito

    Posted

    Hi jojjelito,

    Have a look again, there is one for matched BC547's vcf

    I build them, so I should know what I am talking about ;) I will take a phote when, I am at home...

    I got a source for CEM Chips in Germany, but I need to find the link if you want it?

    greetz Jonas

    Ahh, I see. I guess I was too quick when just taking a peek while at work. There is no such thing as a free lunch... I dread doing the transistor matching just because I figured I wanted instant gratification :whistle:

    BUT, it will take a while before I get to that stage.

    Feel free to share to the CEM linky. I'm not sure at the moment how many 3379 chips I have - I stashed some 15 years ago being young and foolish. Now I'm not that young anymore :hmm:

    Take care,

    Johan

  11. jojjelito

    Posted

    Hi Jonas and Peter!

    I see that Yves (YUSynth) uses a transistor array for his take on the famous VCF instead of manually matching discrete transistors the way that René Schmitz and later Jörgen Bergfors of Bergfotron fame did it. That would save work!

    After thinking about it over some sleep I decided to keep it as simple as possible: Either use SSM2044 or some other IC I have, or a very simple array-based filter as this will be polyphonic. Also it takes 4xAOUT_NG (expensive, innit?) for control. Add a bipolar PSU and maybe VCAs.

    Either I will use Seppos VCAs (as I already planned ahead and got some PCBs) or I'll use what's already in the CEM chips if I go that route. Or I can attempt a 1-transistor VCA the way Korg did it in the PS-series of synths, but that's less than optimal for sound and control. Good for the low parts count though.

    But, I'll make up a tutorial once I get there for sure. At the moment I'm at the graphing paper stage. Then I need to do some breadboarding...

    Maybe Stophlex has made some progress as I know that he was also looking at an external VCF/VCA box?

    However, the JB Weld has cured enough. Time to do the encoders and LEDs!

  12. stilz&Rumpel

    Posted

    Haha, just add the 808 cowbell and hi-hats and you're almost good to go :thumbsup: But, the 808 has cool toms - they sound almost bongo-like unlike the 909. The main irritation if you build a 9090 is that what seems like half of all the components are used by the toms which are a bit boring.

    Good job on porting the MB-808 variant of MB-SEQ to LPC-17! It's time for a more modern micro that costs less.

    Best of luck, it will be interesting to see the results of your work.

  13. pcbatterij

    Posted

    What you need to do is to find out beyond the shadow of a doubt is which two cables are the 0V (GND) connection. Then connect those two together to the GND of the transformer PSU input of the board.

    The plus of secondary one then goes to one of the 15V inputs that's connected to either plus or minus of the diode bridge. The plus of secondary two goes to the other 15V input. Both of the secondaries will be AC when they are output from the transformer so which is plus, which is minus of the diode bridge won't matter, as long as you have a common ground and connect the two outputs to the two different sides of the diode bridge.

    Your picture is on the small side, but it looks like the dots indicate the plus side of the transformer windings. But, please measure before making the connection!

    Rosch's picture above shows a common dual primary transformer. The cool thing about this is that you can use either input for US voltage, or connect the first zero to neutral, bridge the two 115V and the 0V in the middle, and connect the rightmost 115V to a common 230VAC voltage. OR, you wire up a switch (careful!). The lower side shows the two secondaries. Connect the GNDs of both together for a double voltage (+-9VAC) output and then make sure that the plus outputs goes to either side of the diode bridge.

  14. pcbatterij

    Posted

    maybe a stupid question but what do you mean with beans?

    Oh and yes I am still waiting for the ports from Reichelt (including the fuse holders)

    cheers jef

    Ahh, sorry for using slang. See Urban dictionary for a definition. Seeing this took my back on a trip down memory lane.

    My 9090 is finished, but there's still some touching up to do. The Taiwan Alpha pots I got from Futurlec had some issues with the 1M pots so I need to replace those. Also, I need to switch to shielded (grounded in one end) cable for the pots that control the pitch of the digital sounds as those are very noise-sensitive. And yes, slap on the very nice front panel I got from Julian F. But, electronically it's all working. It sounds fantastic! Far better than any samples I've heard :sorcerer:

  15. pcbatterij

    Posted

    Hiya. I could scrounge up some 2SA798s if you're really needy. I got them way back when I defensively hoarded "exotics" from Futurlec or Electronic Surplus et al. See 2SA 798. They're only 0.61 US a pop. Do yourself a favor and buy a few if you ever plan on doing more DIY.

    In Germany you can try HTV-Service

    The 1SS133 diode over the guarden variety 1N4148 is just being silly. It won't alter the sound. At all. Mouser or HTV-Service carries those if you're fussy. :whistle:

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